Currently, there are two main methods used for the construction of concrete buildings:
1. assembling individual casings on each building site, and then pouring the liquid concrete in these casings before it is allowed to set. The delays for constructions in this case are quite lengthy.
2. Providing precast factory-made components, which substantially decrease the time required for in situ assembly of the house. Unfortunately, a significant disadvantage is that heavy machinery is required for this method. Moreover, transportation costs of the factory-made components, and the associated distance between the building site and the extrusion manufacturing facility, become major cost elements.
Major trends in the construction business include a progressive shift from conventional structural components, namely wood, steel and aluminum, toward extruded plastic material-based panel products having enhanced value added factory-made features, increased durability, decreased maintenance requirements and major domestic energy consumption savings features. PolyVinyl Chloride (PVC) is particularly appreciated, since it is cost effective: having 56% of chloride in weight (supplied from halite) and only 44% of hydrocarbons, PVC will be less cost-sensitive than other plastic materials to the cyclical variations in the market prices of petroleum products and of ethylene in particular.
Such plastic based wall panels are desirable, because of their resistance to weather, to impacting and to abrasive forces, because they have a good loading resistance relative to its weight, a very high resistance to the destructive action of chemical agents and a good resistance to combustion, rust, salt, insect damages, and rot. These plastic panels apply not only to domestic buildings or houses, but also to industrial, commercial and institutional buildings, and not excluding gazebos, partitions, sound barriers along highways, farm buildings and barns, and sheds.
Canadian patent application No 2,070,079 published Nov. 30, 1993 in the name of Vittorio DE ZEN, discloses a building constructed of extruded, thermoplastic, structural components. The building is based on a system of factory-made components developed in such a way as to include all the components required for the assembly on the building site of a house with unskilled labour. The extruded modular components are edgewisely interlocked to one another to form continuous, flat wall panels for forming the upright walls and roof parts of the building. More particularly, the side walls and roof panels are said to be configured to be connected into the housing structure by interlocking mating engagement with adjoining members so that they can be assembled without the use of tools. Each wall panel is hollow, is made from PVC plastic material, and consists of spaced exterior and interior walls connected by transverse webs forming internal cells.
Such a wall panel system is lightweight and very easy to assemble by unskilled labour. It appears basically as a casing into which concrete is poured to form smooth, aesthetically appealing interior and exterior plastic wall faces which require minimal maintenance compared to houses built according to different standards.
On the building sites, after assembly of the hollow wall panels, the internal cells can then be filled with uncured (liquid) concrete and.backslash.or a flowable thermal insulation material. Hence, a self-supporting structure can be erected and anchored to a base and converted into a permanent and sturdy structure.
The De Zen structural components as disclosed include extruded hollow panels, extruded hollow pane box connectors, extruded hollow beams and adapters, and extruded panel connectors. All these structural components are factory made, so that they can be assembled on the building sites by unskilled workers in a short period of time. Interior and exterior doors, windows, electrical and plumbing lines, cupboards, and other building elements can be accommodated by this system.
An important disadvantage of such hollow extruded panels pertains to their transportation to the building site: since they are hollow, they take a relatively important volume in the truck van storage area, i.e. a lot of empty space trapped by the hollow panels is wasted during shipping thereof.
In particular, within the new commercial environment created by the North American Free Trade Agreement (NAFTA), trade barriers such as tariffs between Canada, the United States and Mexico have disappeared or are in the process of disappearing. Accordingly, the importance of transportation costs of building components have increased as a percentage of the total costs of building constructions.
U.S. Pat. No. 3,992,839 issued Nov. 23, 1976 to the Ethyl Corporation, also discloses hollow extruded wall members, which are interconnected by transversely extending integral male and female connectors. More particularly, each wall member includes two main parallel wall panels spaced from one another by the transverse connectors. The male connector forms an arrow shape stud, while the female connector forms a complementary socket. The male and female connector elements interlock horizontally with one another in snap-on or clipping, generally unadjustable fashion, along interconnecting axes being orthogonal to that of the parallel (interior and exterior) side wall panels. Additional open tubular corner connector beams are provided, to interlock two adjacent wall members at a 90.degree. degree relative to one another.
One disadvantage of such an extruded wall system as in the Ethyl patent, is that substantial volume is once again wasted during shipping of the corner connector beams, since again, these corner connectors circumscribe a hollow. Moreover, because the axes of interconnection of the wall panels are orthogonal to the planes of the wall panels, a separate corner connector element is required to interlock the two adjacent corner wall panels, thus increasing the total number of wall components required for assembling the building. Thirdly, such transverse connector studs are more likely to be accidentally damaged during handling thereof in the shipping process, because they protrude from the main panel walls, and because they are of the snap-on type. Also, relative adjustment of the panels is difficult, because once the male and female connectors are clipped together, they are not designed to be thereafter relatively movable.